diff --git a/apps/web/src/components/ChatView.tsx b/apps/web/src/components/ChatView.tsx
index fbd332354a..39c3ceaa97 100644
--- a/apps/web/src/components/ChatView.tsx
+++ b/apps/web/src/components/ChatView.tsx
@@ -27,6 +27,7 @@ import { useCallback, useEffect, useLayoutEffect, useMemo, useRef, useState } fr
 import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
 import { useDebouncedValue } from "@tanstack/react-pacer";
 import { useNavigate, useSearch } from "@tanstack/react-router";
+import { COLORBLIND_DIFF_STYLES } from "~/lib/diffRendering";
 import { gitBranchesQueryOptions, gitCreateWorktreeMutationOptions } from "~/lib/gitReactQuery";
 import { projectSearchEntriesQueryOptions } from "~/lib/projectReactQuery";
 import { serverConfigQueryOptions, serverQueryKeys } from "~/lib/serverReactQuery";
@@ -263,6 +264,7 @@ export default function ChatView({ threadId }: ChatViewProps) {
     select: (params) => parseDiffRouteSearch(params),
   });
   const { resolvedTheme } = useTheme();
+  const colorblindStyle = settings.colorblindMode ? COLORBLIND_DIFF_STYLES[resolvedTheme] : null;
   const queryClient = useQueryClient();
   const createWorktreeMutation = useMutation(gitCreateWorktreeMutationOptions({ queryClient }));
   const composerDraft = useComposerThreadDraft(threadId);
@@ -3655,6 +3657,7 @@ export default function ChatView({ threadId }: ChatViewProps) {
                 onImageExpand={onExpandTimelineImage}
                 markdownCwd={gitCwd ?? undefined}
                 resolvedTheme={resolvedTheme}
+                colorblindStyle={colorblindStyle}
                 timestampFormat={timestampFormat}
                 workspaceRoot={activeProject?.cwd ?? undefined}
               />
diff --git a/apps/web/src/components/DiffPanel.tsx b/apps/web/src/components/DiffPanel.tsx
index fadb8cb69d..c47d5af704 100644
--- a/apps/web/src/components/DiffPanel.tsx
+++ b/apps/web/src/components/DiffPanel.tsx
@@ -26,8 +26,11 @@ import { readNativeApi } from "../nativeApi";
 import { resolvePathLinkTarget } from "../terminal-links";
 import { parseDiffRouteSearch, stripDiffSearchParams } from "../diffRouteSearch";
 import { useTheme } from "../hooks/useTheme";
-import { buildPatchCacheKey } from "../lib/diffRendering";
-import { resolveDiffThemeName } from "../lib/diffRendering";
+import {
+  buildPatchCacheKey,
+  COLORBLIND_DIFF_STYLES,
+  resolveDiffThemeName,
+} from "../lib/diffRendering";
 import { useTurnDiffSummaries } from "../hooks/useTurnDiffSummaries";
 import { useStore } from "../store";
 import { useSettings } from "../hooks/useSettings";
@@ -38,7 +41,12 @@ import { ToggleGroup, Toggle } from "./ui/toggle-group";
 type DiffRenderMode = "stacked" | "split";
 type DiffThemeType = "light" | "dark";
 
-const DIFF_PANEL_UNSAFE_CSS = `
+function buildDiffPanelCss(colorblind: boolean, theme: "light" | "dark"): string {
+  const cb = colorblind ? COLORBLIND_DIFF_STYLES[theme] : null;
+  const addition = cb ? cb.addition.color : "var(--success)";
+  const deletion = cb ? cb.deletion.color : "var(--destructive)";
+
+  return `
 [data-diffs-header],
 [data-diff],
 [data-file],
@@ -55,23 +63,23 @@ const DIFF_PANEL_UNSAFE_CSS = `
   --diffs-bg-separator-override: color-mix(in srgb, var(--background) 95%, var(--foreground));
   --diffs-bg-buffer-override: color-mix(in srgb, var(--background) 90%, var(--foreground));
 
-  --diffs-bg-addition-override: color-mix(in srgb, var(--background) 92%, var(--success));
-  --diffs-bg-addition-number-override: color-mix(in srgb, var(--background) 88%, var(--success));
-  --diffs-bg-addition-hover-override: color-mix(in srgb, var(--background) 85%, var(--success));
-  --diffs-bg-addition-emphasis-override: color-mix(in srgb, var(--background) 80%, var(--success));
-
-  --diffs-bg-deletion-override: color-mix(in srgb, var(--background) 92%, var(--destructive));
-  --diffs-bg-deletion-number-override: color-mix(in srgb, var(--background) 88%, var(--destructive));
-  --diffs-bg-deletion-hover-override: color-mix(in srgb, var(--background) 85%, var(--destructive));
-  --diffs-bg-deletion-emphasis-override: color-mix(
-    in srgb,
-    var(--background) 80%,
-    var(--destructive)
-  );
+  --diffs-addition-color-override: ${addition};
+  --diffs-bg-addition-override: color-mix(in srgb, var(--background) 92%, ${addition});
+  --diffs-bg-addition-number-override: color-mix(in srgb, var(--background) 88%, ${addition});
+  --diffs-bg-addition-hover-override: color-mix(in srgb, var(--background) 85%, ${addition});
+  --diffs-bg-addition-emphasis-override: color-mix(in srgb, var(--background) 80%, ${addition});
+
+  --diffs-deletion-color-override: ${deletion};
+  --diffs-bg-deletion-override: color-mix(in srgb, var(--background) 92%, ${deletion});
+  --diffs-bg-deletion-number-override: color-mix(in srgb, var(--background) 88%, ${deletion});
+  --diffs-bg-deletion-hover-override: color-mix(in srgb, var(--background) 85%, ${deletion});
+  --diffs-bg-deletion-emphasis-override: color-mix(in srgb, var(--background) 80%, ${deletion});
 
   background-color: var(--diffs-bg) !important;
+}`;
 }
 
+const DIFF_PANEL_STATIC_CSS = `
 [data-file-info] {
   background-color: color-mix(in srgb, var(--card) 94%, var(--foreground)) !important;
   border-block-color: var(--border) !important;
@@ -169,6 +177,10 @@ export default function DiffPanel({ mode = "inline" }: DiffPanelProps) {
   const settings = useSettings();
   const [diffRenderMode, setDiffRenderMode] = useState<DiffRenderMode>("stacked");
   const [diffWordWrap, setDiffWordWrap] = useState(settings.diffWordWrap);
+  const diffUnsafeCss = useMemo(
+    () => buildDiffPanelCss(settings.colorblindMode, resolvedTheme) + DIFF_PANEL_STATIC_CSS,
+    [settings.colorblindMode, resolvedTheme],
+  );
   const patchViewportRef = useRef<HTMLDivElement>(null);
   const turnStripRef = useRef<HTMLDivElement>(null);
   const previousDiffOpenRef = useRef(false);
@@ -615,7 +627,7 @@ export default function DiffPanel({ mode = "inline" }: DiffPanelProps) {
                           overflow: diffWordWrap ? "wrap" : "scroll",
                           theme: resolveDiffThemeName(resolvedTheme),
                           themeType: resolvedTheme as DiffThemeType,
-                          unsafeCSS: DIFF_PANEL_UNSAFE_CSS,
+                          unsafeCSS: diffUnsafeCss,
                         }}
                       />
                     </div>
diff --git a/apps/web/src/components/GitActionsControl.tsx b/apps/web/src/components/GitActionsControl.tsx
index 1593a151da..0bdd89d68d 100644
--- a/apps/web/src/components/GitActionsControl.tsx
+++ b/apps/web/src/components/GitActionsControl.tsx
@@ -50,6 +50,9 @@ import {
 import { randomUUID } from "~/lib/utils";
 import { resolvePathLinkTarget } from "~/terminal-links";
 import { readNativeApi } from "~/nativeApi";
+import { useSettings } from "~/hooks/useSettings";
+import { useTheme } from "~/hooks/useTheme";
+import { COLORBLIND_DIFF_STYLES } from "~/lib/diffRendering";
 
 interface GitActionsControlProps {
   gitCwd: string | null;
@@ -204,6 +207,9 @@ function GitQuickActionIcon({ quickAction }: { quickAction: GitQuickAction }) {
 }
 
 export default function GitActionsControl({ gitCwd, activeThreadId }: GitActionsControlProps) {
+  const { colorblindMode } = useSettings();
+  const { resolvedTheme } = useTheme();
+  const cb = colorblindMode ? COLORBLIND_DIFF_STYLES[resolvedTheme] : null;
   const threadToastData = useMemo(
     () => (activeThreadId ? { threadId: activeThreadId } : undefined),
     [activeThreadId],
@@ -970,9 +976,19 @@ export default function GitActionsControl({ gitCwd, activeThreadId }: GitActions
                                     <span className="text-muted-foreground">Excluded</span>
                                   ) : (
                                     <>
-                                      <span className="text-success">+{file.insertions}</span>
+                                      <span
+                                        className={cb ? undefined : "text-success"}
+                                        style={cb?.addition}
+                                      >
+                                        +{file.insertions}
+                                      </span>
                                       <span className="text-muted-foreground"> / </span>
-                                      <span className="text-destructive">-{file.deletions}</span>
+                                      <span
+                                        className={cb ? undefined : "text-destructive"}
+                                        style={cb?.deletion}
+                                      >
+                                        -{file.deletions}
+                                      </span>
                                     </>
                                   )}
                                 </span>
@@ -983,11 +999,11 @@ export default function GitActionsControl({ gitCwd, activeThreadId }: GitActions
                       </div>
                     </ScrollArea>
                     <div className="flex justify-end font-mono">
-                      <span className="text-success">
+                      <span className={cb ? undefined : "text-success"} style={cb?.addition}>
                         +{selectedFiles.reduce((sum, f) => sum + f.insertions, 0)}
                       </span>
                       <span className="text-muted-foreground"> / </span>
-                      <span className="text-destructive">
+                      <span className={cb ? undefined : "text-destructive"} style={cb?.deletion}>
                         -{selectedFiles.reduce((sum, f) => sum + f.deletions, 0)}
                       </span>
                     </div>
diff --git a/apps/web/src/components/chat/ChangedFilesTree.tsx b/apps/web/src/components/chat/ChangedFilesTree.tsx
index 0174a77088..fefd00a207 100644
--- a/apps/web/src/components/chat/ChangedFilesTree.tsx
+++ b/apps/web/src/components/chat/ChangedFilesTree.tsx
@@ -6,15 +6,18 @@ import { ChevronRightIcon, FolderIcon, FolderClosedIcon } from "lucide-react";
 import { cn } from "~/lib/utils";
 import { DiffStatLabel, hasNonZeroStat } from "./DiffStatLabel";
 import { VscodeEntryIcon } from "./VscodeEntryIcon";
+import type { ColorblindDiffStyle } from "~/lib/diffRendering";
 
 export const ChangedFilesTree = memo(function ChangedFilesTree(props: {
   turnId: TurnId;
   files: ReadonlyArray<TurnDiffFileChange>;
   allDirectoriesExpanded: boolean;
   resolvedTheme: "light" | "dark";
+  colorblindStyle?: ColorblindDiffStyle | null | undefined;
   onOpenTurnDiff: (turnId: TurnId, filePath?: string) => void;
 }) {
-  const { files, allDirectoriesExpanded, onOpenTurnDiff, resolvedTheme, turnId } = props;
+  const { files, allDirectoriesExpanded, onOpenTurnDiff, resolvedTheme, colorblindStyle, turnId } =
+    props;
   const treeNodes = useMemo(() => buildTurnDiffTree(files), [files]);
   const directoryPathsKey = useMemo(
     () => collectDirectoryPaths(treeNodes).join("\u0000"),
@@ -71,7 +74,11 @@ export const ChangedFilesTree = memo(function ChangedFilesTree(props: {
             </span>
             {hasNonZeroStat(node.stat) && (
               <span className="ml-auto shrink-0 font-mono text-[10px] tabular-nums">
-                <DiffStatLabel additions={node.stat.additions} deletions={node.stat.deletions} />
+                <DiffStatLabel
+                  additions={node.stat.additions}
+                  deletions={node.stat.deletions}
+                  colorblindStyle={colorblindStyle}
+                />
               </span>
             )}
           </button>
@@ -104,7 +111,11 @@ export const ChangedFilesTree = memo(function ChangedFilesTree(props: {
         </span>
         {node.stat && (
           <span className="ml-auto shrink-0 font-mono text-[10px] tabular-nums">
-            <DiffStatLabel additions={node.stat.additions} deletions={node.stat.deletions} />
+            <DiffStatLabel
+              additions={node.stat.additions}
+              deletions={node.stat.deletions}
+              colorblindStyle={colorblindStyle}
+            />
           </span>
         )}
       </button>
diff --git a/apps/web/src/components/chat/DiffStatLabel.tsx b/apps/web/src/components/chat/DiffStatLabel.tsx
index 2dda06fd9d..e098066b1e 100644
--- a/apps/web/src/components/chat/DiffStatLabel.tsx
+++ b/apps/web/src/components/chat/DiffStatLabel.tsx
@@ -1,4 +1,5 @@
 import { memo } from "react";
+import type { ColorblindDiffStyle } from "~/lib/diffRendering";
 
 export function hasNonZeroStat(stat: { additions: number; deletions: number }): boolean {
   return stat.additions > 0 || stat.deletions > 0;
@@ -8,14 +9,24 @@ export const DiffStatLabel = memo(function DiffStatLabel(props: {
   additions: number;
   deletions: number;
   showParentheses?: boolean;
+  colorblindStyle?: ColorblindDiffStyle | null | undefined;
 }) {
-  const { additions, deletions, showParentheses = false } = props;
+  const { additions, deletions, showParentheses = false, colorblindStyle: cb } = props;
+
   return (
     <>
       {showParentheses && <span className="text-muted-foreground/70">(</span>}
-      <span className="text-success">+{additions}</span>
+      {cb ? (
+        <span style={cb.addition}>+{additions}</span>
+      ) : (
+        <span className="text-success">+{additions}</span>
+      )}
       <span className="mx-0.5 text-muted-foreground/70">/</span>
-      <span className="text-destructive">-{deletions}</span>
+      {cb ? (
+        <span style={cb.deletion}>-{deletions}</span>
+      ) : (
+        <span className="text-destructive">-{deletions}</span>
+      )}
       {showParentheses && <span className="text-muted-foreground/70">)</span>}
     </>
   );
diff --git a/apps/web/src/components/chat/MessagesTimeline.tsx b/apps/web/src/components/chat/MessagesTimeline.tsx
index f3174030ef..c468188c8b 100644
--- a/apps/web/src/components/chat/MessagesTimeline.tsx
+++ b/apps/web/src/components/chat/MessagesTimeline.tsx
@@ -40,6 +40,7 @@ import { buildExpandedImagePreview, ExpandedImagePreview } from "./ExpandedImage
 import { ProposedPlanCard } from "./ProposedPlanCard";
 import { ChangedFilesTree } from "./ChangedFilesTree";
 import { DiffStatLabel, hasNonZeroStat } from "./DiffStatLabel";
+import type { ColorblindDiffStyle } from "~/lib/diffRendering";
 import { MessageCopyButton } from "./MessageCopyButton";
 import { computeMessageDurationStart, normalizeCompactToolLabel } from "./MessagesTimeline.logic";
 import { TerminalContextInlineChip } from "./TerminalContextInlineChip";
@@ -79,6 +80,7 @@ interface MessagesTimelineProps {
   onImageExpand: (preview: ExpandedImagePreview) => void;
   markdownCwd: string | undefined;
   resolvedTheme: "light" | "dark";
+  colorblindStyle?: ColorblindDiffStyle | null | undefined;
   timestampFormat: TimestampFormat;
   workspaceRoot: string | undefined;
 }
@@ -103,6 +105,7 @@ export const MessagesTimeline = memo(function MessagesTimeline({
   onImageExpand,
   markdownCwd,
   resolvedTheme,
+  colorblindStyle,
   timestampFormat,
   workspaceRoot,
 }: MessagesTimelineProps) {
@@ -474,6 +477,7 @@ export const MessagesTimeline = memo(function MessagesTimeline({
                               <DiffStatLabel
                                 additions={summaryStat.additions}
                                 deletions={summaryStat.deletions}
+                                colorblindStyle={colorblindStyle}
                               />
                             </>
                           )}
@@ -505,6 +509,7 @@ export const MessagesTimeline = memo(function MessagesTimeline({
                         files={checkpointFiles}
                         allDirectoriesExpanded={allDirectoriesExpanded}
                         resolvedTheme={resolvedTheme}
+                        colorblindStyle={colorblindStyle}
                         onOpenTurnDiff={onOpenTurnDiff}
                       />
                     </div>
diff --git a/apps/web/src/components/settings/SettingsPanels.tsx b/apps/web/src/components/settings/SettingsPanels.tsx
index f9fdb1d615..14c2ba8e50 100644
--- a/apps/web/src/components/settings/SettingsPanels.tsx
+++ b/apps/web/src/components/settings/SettingsPanels.tsx
@@ -459,6 +459,9 @@ export function useSettingsRestore(onRestored?: () => void) {
       ...(settings.timestampFormat !== DEFAULT_UNIFIED_SETTINGS.timestampFormat
         ? ["Time format"]
         : []),
+      ...(settings.colorblindMode !== DEFAULT_UNIFIED_SETTINGS.colorblindMode
+        ? ["Colorblind mode"]
+        : []),
       ...(settings.diffWordWrap !== DEFAULT_UNIFIED_SETTINGS.diffWordWrap
         ? ["Diff line wrapping"]
         : []),
@@ -480,6 +483,7 @@ export function useSettingsRestore(onRestored?: () => void) {
     [
       areProviderSettingsDirty,
       isGitWritingModelDirty,
+      settings.colorblindMode,
       settings.confirmThreadArchive,
       settings.confirmThreadDelete,
       settings.defaultThreadEnvMode,
@@ -837,6 +841,30 @@ export function GeneralSettingsPanel() {
           }
         />
 
+        <SettingsRow
+          title="Colorblind mode"
+          description="Replace red/green with blue/orange across diffs and stats."
+          resetAction={
+            settings.colorblindMode !== DEFAULT_UNIFIED_SETTINGS.colorblindMode ? (
+              <SettingResetButton
+                label="colorblind mode"
+                onClick={() =>
+                  updateSettings({
+                    colorblindMode: DEFAULT_UNIFIED_SETTINGS.colorblindMode,
+                  })
+                }
+              />
+            ) : null
+          }
+          control={
+            <Switch
+              checked={settings.colorblindMode}
+              onCheckedChange={(checked) => updateSettings({ colorblindMode: Boolean(checked) })}
+              aria-label="Enable colorblind mode"
+            />
+          }
+        />
+
         <SettingsRow
           title="Assistant output"
           description="Show token-by-token output while a response is in progress."
diff --git a/apps/web/src/hooks/useSettings.test.ts b/apps/web/src/hooks/useSettings.test.ts
index 832ee17f7f..9844878e1f 100644
--- a/apps/web/src/hooks/useSettings.test.ts
+++ b/apps/web/src/hooks/useSettings.test.ts
@@ -13,4 +13,8 @@ describe("buildLegacyClientSettingsMigrationPatch", () => {
       confirmThreadDelete: false,
     });
   });
+
+  it("does not migrate colorblindMode since it never existed in legacy settings", () => {
+    expect(buildLegacyClientSettingsMigrationPatch({ colorblindMode: true })).toEqual({});
+  });
 });
diff --git a/apps/web/src/lib/diffRendering.ts b/apps/web/src/lib/diffRendering.ts
index 7218f72978..f2204b6af0 100644
--- a/apps/web/src/lib/diffRendering.ts
+++ b/apps/web/src/lib/diffRendering.ts
@@ -1,3 +1,20 @@
+// GitHub Primer colorblind palette (protanopia/deuteranopia).
+// Source: @primer/primitives diffBlob tokens.
+// Light: addition #0969da (blue), deletion #bc4c00 (orange)
+// Dark:  addition #388bfd (blue), deletion #db6d28 (orange)
+export const COLORBLIND_DIFF_STYLES = {
+  light: {
+    addition: { color: "#0969da" } as const,
+    deletion: { color: "#bc4c00" } as const,
+  },
+  dark: {
+    addition: { color: "#388bfd" } as const,
+    deletion: { color: "#db6d28" } as const,
+  },
+} as const;
+
+export type ColorblindDiffStyle = (typeof COLORBLIND_DIFF_STYLES)["light" | "dark"];
+
 export const DIFF_THEME_NAMES = {
   light: "pierre-light",
   dark: "pierre-dark",
diff --git a/packages/contracts/src/settings.test.ts b/packages/contracts/src/settings.test.ts
index e7f638c7f3..9a4414072d 100644
--- a/packages/contracts/src/settings.test.ts
+++ b/packages/contracts/src/settings.test.ts
@@ -5,4 +5,8 @@ describe("DEFAULT_CLIENT_SETTINGS", () => {
   it("includes archive confirmation with a false default", () => {
     expect(DEFAULT_CLIENT_SETTINGS.confirmThreadArchive).toBe(false);
   });
+
+  it("includes colorblind mode with a false default", () => {
+    expect(DEFAULT_CLIENT_SETTINGS.colorblindMode).toBe(false);
+  });
 });
diff --git a/packages/contracts/src/settings.ts b/packages/contracts/src/settings.ts
index 9cd8a5f251..36b7aee19b 100644
--- a/packages/contracts/src/settings.ts
+++ b/packages/contracts/src/settings.ts
@@ -24,6 +24,7 @@ export type SidebarThreadSortOrder = typeof SidebarThreadSortOrder.Type;
 export const DEFAULT_SIDEBAR_THREAD_SORT_ORDER: SidebarThreadSortOrder = "updated_at";
 
 export const ClientSettingsSchema = Schema.Struct({
+  colorblindMode: Schema.Boolean.pipe(Schema.withDecodingDefault(() => false)),
   confirmThreadArchive: Schema.Boolean.pipe(Schema.withDecodingDefault(() => false)),
   confirmThreadDelete: Schema.Boolean.pipe(Schema.withDecodingDefault(() => true)),
   diffWordWrap: Schema.Boolean.pipe(Schema.withDecodingDefault(() => false)),